Method for manufacturing a fiber type coupler

ABSTRACT

A method for manufacturing a fiber type coupler or the present invention by fusing and elongating a plurality of optical fibers is characterized in that a multi-wire optical fiber wire is used as the plurality of optical fibers.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method for manufacturing a fiber typecoupler by fusing and elongating a plurality of optical fibers.

2. Related Background Art

FIG. 1 is a block diagram which shows a related background artmanufacturing method of the fiber type coupler. The related backgroundart manufacturing method is now explained. Two optical fiber wires of 50cm length are prepared. Each of the optical fiber wires has a plasticjacket and an RIV (room temperature vulcanized silicon) coating. Thecoatings of the optical fiber wires are partially removed, and theoptical fibers 1 having the coatings partially removed are contacted toeach other and they are fixed by fixing members 2 in the contactedstate. In this case, a photo-sensor 3 and a power meter 4 are connectedto one end of each optical fiber, and a light source 5 is connected tothe other end.

Then, the contacted optical fibers are heated by a burner 6, and amonitoring light from the light source 5 is sensed by the photo-sensors3 and measured by the power meters 4 in order to monitor a split ratioat the coupler area. When the split ratio reaches a desired value, theelongation is stopped and a protective member is molded to form thefiber type coupler (see Japanese PCT published Patent (A) 60-501427).

A vertical adjuster for adjusting a vertical position of the opticalfiber and a horizontal adjustor for adjusting a horizontal position areused, and the optical fibers are positioned vertically and horizontally.(See Japanese Patent Application 59-88166).

However, in the two-direction positioning method described above, thereis a difference among tensile force applied to the optical fibers whenthey are fixed to an optical fiber fixing member. (Refer to JapaneseLaid-Open (KOKAI) Patent Application 63-118705)

FIG. 2 is a perspective view which illustrates an affect of the tensileforce in the fusing process. FIG. 2A shows a fiber type couplermanufactured under a constant tensile force applied during the fusingprocess, and FIG. 2B shows a fiber type coupler manufactured underdifferent tensile force applied during the fusing process. When theapplied tensile forces are different, the coupler is bent at a fusingregion A because the tensile forces are released in the molten state,and a twist is generated. The bend or twist at the fusing region Aincreases an insertion loss of the fiber type coupler. Further, sincethe bending state is not constant, a reproducibility of the fiber typecoupler is low and hence a yield is low.

In order to eliminate the above drawbacks, a manufacturing apparatus hasbeen improved. (See Japanese Laid-Open (KOKAI) Patent Application63-118705). In this apparatus, in the position adjustment process of themanufacture of the fiber type coupler, the optical fibers are fixed to amovable table to which a constant force is applied so that the opticalfibers are positioned under a uniform tensile force applied to theoptical fibers. In this manner, the bend and twist at the fusing areaare reduced.

However, in order to keep the tensile force constant, means forbalancing the tensile forces is additionally required in theconventional manufacturing apparatus. As the diameter of the opticalfiber is reduced, or as the number of wires increases, it becomes harderto keep the tensile forces uniform and a higher precision control isrequired. As a result, the cost of the apparatus rises.

In the related background art manufacturing method of the fiber typecoupler, the photo-sensor must be connected to one end of the opticalfiber. As a result, the workability in the mass production is poor.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a manufacturingmethod which can simply reduce the bend and twist in the fusing andelongating processes, attains high reproducibility and improves amanufacturing yield.

It is other object of the present invention to improve a work efficiencyin a manufacturing process of the fiber type coupler.

In order to achieve the above objects, the method for manufacturing afiber type coupler of the present invention by fusing and elongating aplurality of optical fibers is characterized in that a multi-wireoptical fiber wire is used as said plurality of optical fibers.

In accordance with the present invention, the process time tomanufacture the fiber type coupler is shortened. In the mass productionprocess, a significant process time is shortened by shortening theprocess time to manufacture the individual fiber type couplers.

The present invention will become more fully understood from thedetailed description given hereinbelow and the accompanying drawingswhich are given by way of illustration only, and thus are not to beconsidered as limiting the present invention.

Further scope of applicability of the present invention will becomeapparent from the detailed description given hereinafter. However, itshould be understood that the detailed description and specificexamples, while indicating preferred embodiments of the invention, aregiven by way of illustration only, since various changes andmodifications within the spirit and scope of the invention will becomeapparent to those skilled in the art from this detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a related background art method formanufacturing the fiber type coupler,

FIG. 2A and 2B illustrate an affect of a tensile force in a fusingprocess,

FIG. 3 shows a flow chart of a method for manufacturing a fiber typecoupler in accordance with one embodiment of the present invention,

FIGS. 4A to 4F show process charts of the method for manufacturing thefiber type coupler in accordance with the one embodiment of the presentinvention,

FIG. 5 illustrates a monitoring method applicable to the method formanufacturing the fiber type coupler of the present invention,

FIGS. 6A and 6B are graphs showing a result of an experiment for thepresent invention,

FIG. 7 shows a flow chart of a method for manufacturing a fiber typecoupler in accordance with one embodiment of the present invention, and

FIGS. 8A to 8E show manufacturing process charts of the fiber typecoupler of the one embodiment.

FIG. 9A is a sectional view of a bobbin for the structure of an opticalrotary joint.

FIG. 9B is a sectional view of a bobbin for the structure of a slipring.

DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 3 shows a flow chart of the method for manufacturing the fiber typecoupler of the present embodiment, and FIG. 4A to 4F show process chartsof the fiber type coupler of the present embodiment.

In a step 101, a plurality of optical fiber elementary wires 6 havingprimary coating applied thereon are arranged in parallel to each otheralong a longitudinal direction (optical axis) (see FIG. 4A), and acoating 7 is applied to integrate the wires 1 under the same tensileforce (see FIG. 4B). The optical fibers to be integrated may be opticalfibers having no primary coating applied thereto or optical fibershaving secondary coating applied thereto. What is important is that theoptical fibers are fixed under the constant tensile force. Accordingly,for example, two coated optical fibers may be supplied under the sametensile force to form an integrated multi-wire optical fiber wire (seeJapanese Laid-Open (KOKAI) Patent Application 61-63810). The opticalfiber elementary wires 6 to be integrated need not necessarily bearranged in parallel to each other.

In a step 102, the coating 7 of the integrated multi-wire optical fiberwire and the primary coatings of the optical fiber elementary wires 6are partially removed (see FIG. 4C), and the stripped optical fibers 6are positioned in two directions so that they are fixed in a contactstate (step 103). Specifically, they are horizontally positioned byhorizontal positioning members 8, 9, 10 and 11, and verticallypositioned by vertical positioning members 12, 13, 14 and 15 (see FIG.4D).

In a step 104, the contacted optical fibers 6 are fused by an acetyleneburner 16 and the fused region are elongated along the optical axis (seeFIG. 4E). For example, as shown in FIG. 5, LED light sources 7 and 8 areconnected to the first ends of the optical fibers 6, power meters (PM) 9and 20 are connected to the second ends, and three burners 21, 22 and 23which function as heaters are arranged along the optical axis. A splitratio in the fuse-elongation process is monitored (step 105). When thesplit ratio reaches a predetermined value, the extension is stopped(step 106), but if the split ratio does not reach the predeterminedvalue, the fuse (or heat)-elongation process is continued (step 104). Inthe step 106, the fiber type coupler is manufactured (see FIG. 4F).

The present invention is not limited to the above embodiment. Forexample, the number of optical fibers is not limited to two, and asingle mode fiber or multi-mode fiber may be used.

A dispersion-shifted fiber having a zero dispersion wavelength shiftedto 1.55 μm at which a quartz optical fiber exhibits a minimum loss maybe used as the optical fiber.

A result of experiment for the present invention is now explained. Inthe experiment, a two-wire web type optical fiber wire having twooptical fiber elementary wires integrated parallelly was manufactured,and a loss in the fusing process of the optical fibers was measured. Themanufacturing condition of the fiber type coupler used in the experimentis first explained.

The optical fiber elementary wires used for the fiber type coupler ofthe present invention were single mode fibers having MFD of 9.5±1 μm andnormal wavelength of 1.3 μm. They were finished by ultraviolet ray curedresin to have an 250 μm. Those optical fiber elementary wires werearranged at a predetermined pitch, and finished by ultraviolet ray curedresin to have a width of 0.6 mm and a thickness of 0.4 mm. A web of a300 meters length was manufactured at a taping tensile force of 50±2grams, and a fiber velocity of 40 meters/minute. A fusing condition informing the fiber type coupler was a clamping pitch of 8 mm and an LEDlight source having a wavelength of 1.3 μm. As the heater, three burnershaving a bore diameter of 0.2 mm which used acetylene-oxygen (acetylene1 cm³ /min, oxygen 30 cm² /min) as combustion gas were arranged alongthe optical axis (see FIG. 5). The three burners were arranged at theintervals of 5 mm, 3 mm and 5 mm, and the fusing time was 30 seconds.

Regarding the related background art method, two optical fiberelementary wires were fixed one by one with best care to attain uniformtensile force.

FIGS. 6A and 6B show the result of the experiment. A change(attenuation) of a power was calculated based on the light sources andthe power meters connected to the fibers, as a loss in the fused joint,and it is represented as a frequency polygon. FIG. 6A shows that for themanufacturing method of the present invention, and FIG. 6B shows thatfor the related background art manufacturing method. It is seen from theexperiment that the manufacturing method for the fiber type coupler ofthe present invention provide a smaller loss in the fusing process andhigher reproducibility than those of the related background artmanufacturing method.

FIG. 7 shows a flow chart of a method for manufacturing a fiber typecoupler in accordance with another embodiment, and FIG. 8 shows amanufacturing process of the fiber type coupler of the FIG. 7embodiment.

As shown in FIG. 8A, a rotatable bobbin 22 having a plurality of opticalrotary joints 21 attached thereto is prepared. A multi-wire opticalfiber wire 23 is wound on the bobbin 22. A leading end (a start end fromthe bobbin) of the multi-wire optical fiber wire 23 is separated, andindividual optical fibers accommodated in the multi-wire optical fiberwire 23 are connected to the optical rotary joints 21. The opticalrotary joints 21 are also connected to light detectors 24 which comprisephoto-sensors and power meters. The present embodiment is now explained.

in a step 201, the multi-wire optical fiber wire 23 is driven out of thebobbin 22. Since only the rotary portion (not shown) of the bobbin 22having the multi-wire optical fiber wire 23 wound thereon is rotated,the positions of the optical rotary connectors 21 do not change.

In a step 202, an end 23A of the multi-wire optical fiber wire 23 isconnected to a light source 25 (see FIG. 8A). The end may be connecteddirectly to a light emitting device such as an LED, or a monitoringlight may be inputted by connecting a light merger.

In a step 203, a portion of a coating of the driven-out multi-wireoptical fiber wire 23 is removed. Coatings of the optical fiberelementary wires (optical fibers having primary coatings appliedthereto) accommodated in the multi-wire optical fiber wire 23 are alsoremoved. Through the removal of the coatings, the optical fibers areexposed in a stripped state (see FIG. 8B).

In a step 204, the exposed optical fibers 23a and 23b are fixed whilethey are contacted to each other by the fixing members 26 (see FIG. 8C).They may be fixed in two directions orthogonal to the optical axis (forexample, horizontal direction and vertical direction) in order toincrease the fixing force.

In a step 205, the optical fibers are fused by a heater 27 such as anacetylene burner (see FIG. 8D) and the fused region are elongated alongthe optical axis. A plurality of heaters may be arranged along theoptical axis to relieve a temperature distribution applied to theoptical fibers. For example, three heaters may be arranged at theintervals of 3 mm, 5 mm and 3 mm.

In a step 206, whether a predetermined split ratio is reached or not isdetermined by monitoring the light detector. If the predetermined spitratio has not been reached, the fusing and elongation process arefurther continued (step 205). If the predetermined split ratio isreached, the elongation process is stopped (step 207). In this stage, acoupler member 23B of the fiber type coupler is formed (see FIG. 8D).

In a step 208, a protective member 28 is molded and the coupler member23B is fixed (see FIG. 8E). The coupler member 23B is protected by theprotective member 28. The protective member 28 may be formed by applyingthe coating by spraying.

In a step 209, the driven-out multi-wire optical fiber wire 23 is cut ona side of the bobbin (see FIG. 8E) to form the fiber type coupler.

The present invention is not limited to the above embodiment. Forexample, the light source 25 may be connected to a portion of thedriven-out multi-wire optical fiber wire after the portion of thecoating of the multi-wire optical fiber wire 23 has been removed.

As the multi-wire optical fiber wire of the present embodiment, aplurality of optical fibers may be arranged along a line orthogonal tothe optical axis and they may be integrated by a common coating to forma web type optical fiber wire.

In the present embodiment, the optical rotary joints 21 are used at thejunctions of the bobbin 22 and the light detectors 24. Alternatively,the photo-sensors may be mounted on the rotating bobbin and theelectrical signals from the photo-sensors may be supplied to the powermeters through slip rings arranged externally of the bobbin.

FIG. 9A is a sectional view taken along rotational axis of a bobbin forthe structure of an optical rotary joint. A ferrule 31, which isconnected to one end of an optical fiber wire 23, is held by adhesion Bto a ferrule holding member 30 which is fixed to the side wall of abobbin 22. A light detector holding member 33 is attached rotatably tothe opposite side of the ferrule holding member 30 by leaf spring C withball 32 interposed between them. A light detector 24 is held by thelight detector holding member 33 so as to receive the light radiatedfrom the ferrule 31.

According to the optical rotary joint, since the radiated light can bereceived with the large area of light detector 24, the alignment ofoptical axis between ferrule 31 and light detector 24 can be performedwith facility. In this case, ferrule 31 may be connected to a singlemode fiber and the light radiated from the ferrule 31 may be transmittedto light detector 24 through a graded index fiber interposed betweenthem.

FIG. 9B is a sectional view taken along a rotational axis of a bobbinfor the structure of a slip ring. This slip ring comprises slide ring 35and brush 36 in its structure. The slide ring 35 is attached to a ringbase 39 provided with the rotational axis 37 of the bobbin (not shown).The pipe 38 is interposed between the ring base 39 and the rotationalaxis 37. And the brush 36 is fixed to a support 41 fixed to body 40.This body 40 has a fixed terminal board (not shown) on the surface andthe rotational terminal board 42 is arranged beside (right side in FIG.9B) to the body 40 with the pipe 38 interposed between the rotationalterminal board 42 and the rotational axis 37. The rotational terminalboard 42 and the ring base 39 are connected with lead wire 43. Therotational terminal board 42 has many terminals 44 along thecircumference. These terminals 44 are connected to a photodiode (lightdetector) provided with the bobbin. The electrical signal from thephotodiode can be easily transmitted to the fixed terminal board throughthe slip ring.

Further, the optical rotary joint and slip ring are not limited to thedevices having the above structure. For example, FRJ-01, 02, 03 and 03Eof Sumitomo Electric Industries, Ltd. can be used for the optical rotaryjoint and 3TA, 3TBS and 3TC of Meisei Electric Corporation Inc. can beused for the slip ring.

A result of an experiment for the present invention is now explained. Inthe experiment, two conventional optical fiber elementary wires for 1.3μm wavelength communication (outer diameter 125 μm, MFD 9.5±1 μm, cutoffwavelength 1.2 to 1.3 μm), coated by ultraviolet ray cured resin wereintegrated by a common coating of ultraviolet ray cured resin to form aweb type optical fiber wire of 1 km long. The web type optical fiberwire was wound on a plastic bobbin having a drum diameter of 280 mm. Twooptical rotary joints were mounted on the plastic bobbin. A single-wirecord of graded index fiber having a clad diameter of 125 μm, a corediameter of 50 μm and a refractive index of 1% was used to connect theoptical rotary joints to the light detector.

A change of loss when the optical fiber was driven out by 20 meters wasonly 0.05 dB. Insertion losses of the two optical rotary joints weremeasured by a cutback method. The difference thereof was 0.02 dB whichis of sufficient precision for monitoring the split ratio.

From the invention thus described, it will be obvious that the inventionmay be varied in many ways. Such variations are not to be regarded as adeparture from the spirit and scope of the invention, and all suchmodifications as would be obvious to one skilled in the art are intendedto be included within the scope of the following claims.

We claim:
 1. A method for manufacturing a fiber type coupler by fusingand elongating a plurality of optical fibers werein a multi-wire opticalfiber wire is employed as said plurality of optical fibers and whereinsaid multi-wire optical fiber wire is wound on a rotatable bobbin andconnected to a light detector through an optical rotary joint.
 2. Amethod for manufacturing a fiber type coupler by fusing and elongating aplurality of optical fibers wherein a multi-wire optical fiber wire isemployed as said plurality of optical fibers and wherein said multi-wireoptical fiber wire is wound on a rotatable bobbin and connected to apower meter through a photo-sensor and a slip ring.
 3. A method formanufacturing a fiber type coupler according to claim 2 wherein saidoptical fiber group is a web type optical fiber wire.
 4. A method formanufacturing a fiber type coupler according to claim 3 wherein saidplurality of optical fibers are integrated under the same state ofapplying a same tensile force along the optical axis of each of theplurality of optical fibers.
 5. A method for manufacturing a fiber typecoupler according to claim 2 wherein said plurality of optical fibersare dispersion-shifted fibers.
 6. A method for manufacturing a fibertype coupler according to claim 2 wherein said plurality of opticalfibers are quartz dispersion-shifted fibers having zero dispersionwavelength to 1.55 μm.
 7. A method for manufacturing a fiber typecoupler by fusing and elongating a plurality of optical fibers wherein amulti-wire optical fiber wire is employed as said plurality of opticalfibers, said method comprising:a first step of driving out saidmulti-wire optical fiber wire connected to a light detector through anoptical rotary joint and wound on a rotatable bobbin; a second step ofconnecting a light source to a portion of the driven-out multi-wireoptical fiber wire; a third step of removing a portion of coating of themulti-wire optical fiber wire having the light source connected theretoto expose optical fibers accommodated in the multi-wire optical fiberwire; a fourth step of fixing the optical fiber in a mutual contactstate and fusing and elongating the optical fibers to form a couplermember, and a fifth step of fixing the coupler member by a protectivemember and cutting the multi-wire optical fiber wire on the side of thebobbin.
 8. A method for manufacturing a fiber type coupler according toclaim 7 wherein said multi-wire optical fiber wire is a web type opticalfiber wire having a plurality of coated optical fibers arrangedorthogonally to an optical axis and integrated by a common coating.
 9. Amethod for manufacturing a fiber type coupler according to claim 7wherein said optical fiber group is a web type optical fiber wire.
 10. Amethod for manufacturing a fiber type coupler according to claim 8wherein said plurality of optical fibers are integrated under the samestate of applying a same tensile force along the optical axis of each ofthe plurality of optical fibers.
 11. A method for manufacturing a fibertype coupler according to claim 7 wherein said plurality of opticalfibers are dispersion-shifted fibers.
 12. A method for manufacturing afiber type coupler according to claim 7 wherein said plurality ofoptical fibers are quartz dispersion-shifted fibers having zerodispersion wavelength to 1.55 μm.
 13. A method for manufacturing a fibertype coupler by fusing and elongating a plurality of optical fiberswherein a multi-wire optical fiber wire is employed as said plurality ofoptical fibers, said method comprising:a first step of driving out saidmulti-wire optical fiber wire connected to a light detector through anoptical rotary joint and wound on a rotatable bobbin; a second step ofremoving a portion of a coating of the driven-out multi-wire opticalfiber wire to expose the optical fibers accommodated in the multi-wireoptical fiber wire; a third step of connecting a light source to aportion of the driven-out optical fiber wire; a fourth step of fixingthe optical fibers in a mutual contact state and fusing and elongatingthe optical fibers to form a coupler member; and a fifth step of fixingthe coupler member by a protective member and cutting the multi-wireoptical fiber wire on a side of the bobbin.
 14. A method formanufacturing a fiber type coupler according to claim 13 wherein saidoptical fiber group is a web type optical fiber wire.
 15. A method formanufacturing a fiber type coupler according to claim 13 wherein saidplurality of optical fibers are integrated under the same state ofapplying a same tensile force along the optical axis of each of theplurality of optical fibers.
 16. A method for manufacturing a fiber typecoupler according to claim 13 wherein said plurality of optical fibersare dispersion-shifted fibers.
 17. A method for manufacturing a fibertype coupler according to claim 13 wherein said plurality of opticalfibers are quartz dispersion-shifted fibers having zero dispersionwavelength to 1.55 μm.
 18. A method for manufacturing a fiber typecoupler comprising the steps of:providing an optical fiber group havinga plurality of optical fibers, removing partially the coating of theoptical fiber group to expose all of the plurality of optical fiberstherein, pairing and fixing all of the plurality of optical fibers in acontact state, and fusing and elongating the plurality of optical fibersin pairs, wherein said multi-wire optical fiber wire is wound on arotatable bobbin and connected to a light detector through an opticalrotary joint.
 19. A method for manufacturing a fiber type couplercomprising the steps of:providing an optical fiber group having aplurality of optical fibers, removing partially the coating of theoptical fiber group to expose all of the plurality of optical fiberstherein, pairing and fixing all of the plurality of optical fibers in acontact state, and fusing and elongating the plurality of optical fibersin pairs, wherein said multi-wire optical fiber wire is wound on arotatable bobbin and connected to a power meter through a photo-sensorand a slip ring.